Our overall objective is to determine the extent to which light scattering measurements can be used as a tool to probe structures in normal and abnormal corneas. This is to be accomplished by combining light scattering measurements with theoretical analyses based on the structural features determined from electron microscopy (EM), from structure models, or from both. Comparisons test the validity of the structural models, or of the EM, and permit us to relate the cornea's structure to its scattering properties. Indeed we have used this method: to elucidate characteristics of the fibril arrangement in the transparent normal cornea and in turbid swollen corneas, to show that significant reductions in the fibril tension produce a small-angel light scattering pattern, to demonstrate that fibrils are the primary scattering elements at non-specular angles, and to develop a theoretical capability to make quantitative calculations for abnormal corneas. More recently, we created software for a Macintosh II personal computer to automatically process the images shown in electron micrographs and obtain the predicted scattering. Also, we have extended our small- angle polarized light scatter theory to include arbitrary two-dimensional lamella waviness and thickness variations. In addition, we have shown that corneal transplants (with the sutures in place) and radial keratotomies do not produce significant reductions in the central corneal fibril tensions one week post-surgery. Small angle light scattering (SALS) on human corneas did not show a lobed pattern that disappeared with the application of pressure; rather there is a cross-pattern that is present at all pressures and whose orientation does not depend on the polarization direction of the incident beam. Our specific goals are to complete the applications of this methodology to examine fibrillar structures in scar tissue and to obtain more quantitative information in swollen corneas. In addition, quantitative information about lamellar waviness and thickness variations in normal corneas will be obtained using electron microscopy and (scanning-slit) specular microscopy, and will be incorporated in our recently extended SALS theory for comparison with experiments. Success in these studies will give better understanding of the structural basis for the transparency and mechanical properties of normal corneas, and elucidate the factors responsible for the transparency loss in scar tissue.l